Piston clamp



Jan. 9, 1934- c. w. PROCHASKA PISTON CLAMP Filed May 26, 1952 HTTO/QNEY.

Patented Jan. 9, 1934 PISTON CLAMP Carroll W. Prochaska, Mount Vernon, N. 55., as-

signor to Ramsey Accessories Manufacturing Corporation, St. Louis, Missouri Mo., a corporation of Application May 26, 1932. Serial No. 613,699

1 Claim.

The present invention relates to improvements in devices for clamping cylindrical objects such as engine pistons in fixed position for performing operations thereon.

The main object of the invention is to provide a simple, inexpensive and effective device for clamping a piston in position for machining or other similar operations, and in such a manner that the surface thereof which has been finished will not be marred. For instance, it is often desired to widen, narrow, or true up the ring grooves of a piston of an internal combustion engine. Under these conditions, it is necessary to clamp the piston in position so that the circumference of the portion of the piston having ring grooves is entirelyaccessible for the operations that are to be performed thereon. An ordinary vise is not desirable for holding the piston, for the vise will not hold the piston against turning unless considerable pressure be exerted, and this pressure acting on opposite points of the piston surface may roughen the finished surface and impart a permanent distortion to the piston, especially if the piston is of the expansible split skirt type; a further object is to provide a clamping device that is adaptable for various sizes of pistons; another object of the present invention is to provide a clamping device which may be secured in an ordinary vise, and which will rigidly support a piston and at the same time lock it against rotative action.

In a specific embodiment of the present invention, a block is provided which may be easily clamped in a standard vise, and which has inclined supponing surfaces together forming a Y- shaped seat for supporting pistons of various sizes.

As an important feature of the present invention, the piston is held around a portion of its 40 circumference by a flexible strap which is advantageously attached to the block. By means of this arrangement, the clamping pressure is more evenly distributed around the circumference of the piston, thereby eliminating the marring effeats of concentrated clamping pressures on the surface of said piston. Furthermore, by distributing the clamping pressure around a larger area, compression of the cylinder Walls of the piston ten ing to distort said walls is minimized.

As an added feature of the present invention, the cylinder is held against rotative action by an abutment member so positioned that it may extend into one of the pistons apertured bosses for the wrist pin. The piston is thereby held against rotation by positive engaging means independent of the tightness of the frictional engagement of the strap with the piston surface. The effective length of the strap is advantageously made adjustable to accommodate for pistons of various sizes.

Other advantages will be better apparent from a detail description of the invention in connection with the accompanying drawing, in which:

Figure 1 is a perspective view showing a piston clamped in position by a device embodying 5 the present invention, and secured in a standard vise; Fig. 2 is a side elevation of the piston and device shown in Fig. l, the piston, however, being shown dotted; and Fig. 3 is a section taken on line 33 of Fig. 2.

Referring to the drawing, my improved clamp is shown in a form adapted for use in'clamping a standard piston 10 of an internal combustion engine, although as far as the broad aspects of the invention are concerned, it may be adapted for clamping any object having curved surfaces. The piston is shown having the usual series of piston ring grooves 11 atone end thereof, and a pair of diametrically opposed bosses 12 having apertures 13 for receiving a wrist pin, by means of which a piston rod may be connected to said piston.

The clamping device of the present invention includes a metal block 14 for supporting the piston, said block being advantageously Y-shaped and having a shank member 15 adapted to be clamped between the'jaws of a standard vise 16.

To support the piston 10, the block 14 is provided with a pair of arms 17 and 18 diverging from the shank 15 to form a recess 19, and form- 90 ing shoulders 20 at the end of said shank adapted to seat on the top of the vise jaws when mounted in position. These arms 17 and 18 are provided with inclined surfaces 21 for contacting with the outer periphery of the piston at spaced points 22 and 23, and supporting said piston. The inclined surfaces 21 are adapted to support pistons of various sizes, and, if desired, may be lined with soft material such as copper to prevent the marring of the piston surface.

In order to hold the piston against rotation, there is provided a flexible strap 24 made advantageously of spring steel, and adapted to be attached to the block 14. In order to hold this strap 24 in position, the arm 17 extends upwardly beyond arm 18 and has a tapered opening 25 formed in or near its extremity. A screw 26 is riveted or otherwise secured, as shown at h 27, to the strap 24, and said screw is adapted to averse the opening 25. A wing-nut 28 and 11 r f and thereby holds the piston against rotation.

washer 29 are passed over the outer end of screw 26 to adjustably secure the strap to arm 17, and said washer bears on a rounded boss 30 formed on the outer surface of said arm to permit the screw to rock in the tapered opening 25 when the strap is being manipulated.

For detachably securing the strap 24 to the other jaw 18, the latter .is provided with a rounded flange 35 having a pin 36 projecting outwardly and downwardly therefrom. The strap 24 is provided with a plurality of spaced apertures 37, each adapted to be engaged by the pin 36, the particular aperture to be engaged being selected in accordance with the size of the piston to be clamped. In operation, the piston is placed between the jaws in the :desired position, the nut 28 is loosened but not necessarily removed, and the strap is .drawn over the piston, and the appropriate hole 37 is placed over the pin 36. The nut 28 is then tightened until the piston is firmly clamped. It is seen that the strap frictionally engages a substantial portion of "the circumference of the piston, thereby eliminating concentrated clamping pressure, which would distort thepiston skirt or mar the surface.

As an addedfeature of the present invention, the strap is provided with means which positively engages the piston, and prevents rotation thereof when said piston is in clamped position. For this purpose, the strap is provided with a button or stud 40 which is connected to the strap in any suitable manner, as for instance by riveting.

This stud or projection is adapted to extend in oneof the apertures 13 of the'wrist pin bosses 12, It is seen, therefore, that the pressure acting on the outside of the piston through the straps and inclined arms 17 and 18 need not be so great as to insure non-rotation of the piston. It is merely sufficient to give clamping action, the stud'preventing the rotation.

In clamping the piston in position, the strap 24 may be applied, with the stud 40 inserted in the aperture 13. It is not necessary that the stud have a tight fit in the aperture, and it is not necessary that the stud be so positioned that the aperture be at the exact top side of the piston. The stud may operate along any portion of the strap which engages the piston surface. If the strap is not tightened enough to prevent rotation of the piston, the latter may turn only sufficiently to take up the lost motion between the side of the stud and the side of the wrist and the side of the wrist pin aperture.

Obviously, if an object is being clamped that is not provided with an aperture to receive the stud 40 the strap 24 may be reversed with respect to the object being clamped so that the stud 40 will project upwardly instead of downwardly. In this manner the strap is reversible if it is necessary to so use it.

Having described my invention, I claim:

A device for clamping a piston in position to be operated upon, said device including a Y- shaped block having a shank adapted to be engaged between the opposing jaws of a vise, and a pair of arms extending from said shank and presenting therebetween a seat for the piston, said arms forming shoulders with said shank adapted to seat on top of the jaws of the vise when in clamped position, a flexible strap adapted to pass over a portion of the surface of the piston and having a plurality of apertures spaced along the strap at one end thereof, a pin extending from said block and adapted to engage any one of said apertures, a screw member connected to the other end of said strap, the upper end of one of said arms havingan aperture for receiving said screw member, a nut threaded on said screw member and engaging said bracket for tightening said strap around the periphery of said object, and a button projecting from said strap and adapted to extend in an aperture in said cylindrical object to hold said object against rotation.

CARROLL W. PROCHASKA. 

